The invention relates to power drive mechanisms for power operation of a vehicle liftgate.
Minivans and recreational vehicles frequently have rear liftgates that are pivotally mounted to the vehicle frame at the rear of the vehicle. The liftgate is pivotally mounted to the frame by top hinges to allow the liftgate to move between open and closed positions. Manually operated liftgates and power operated liftgates are well known. Power operated liftgates can be opened and closed manually if a vehicle user so desires. Power operated liftgates are typically driven in opening and closing directions by an electrical motor that is operatively engagable with the liftgate through a series of gears., At least one gear is movably mounted for movement between engaging and disengaging positions so that the motor is operatively connected to the liftgate when the gears are engaged so the liftgate can be moved in opening and closing directions by the motor and is disconnected from the liftgate when the gears are disengaged so the liftgate can be opened and closed manually without backdriving the motor. Examples of typical systems include U.S. Pat. Nos. 5,448,856 and 5,563,483.
The movable gear may have a tendency to move out of engagement when the motor is either opening or closing the liftgate, depending on the particular geometry. This is undesirable because movement of the movable gear can result in gear slippage and/or in excessive gear noise.
The disadvantages of the prior art may be overcome by providing a power drive mechanism in which a gear train can be releasably locked or held in driving engagement during power assisted liftgate opening and closing and can be released from driving engagement thereafter to give the vehicle user the option of manually opening or closing the liftgate without backdriving the drive motor.
According to one aspect of the invention, there is provided a power drive mechanism for a driving a liftgate for a vehicle. The vehicle has a body controller controlling the operation of the power drive mechanism. The liftgate has a power operated latch assembly capable of primary and secondary latching engagement with a striker on the vehicle to releasably latch the liftgate and capable of power operated unlatching of the latching assembly. The power drive mechanism has a mounting bracket mountable on a xe2x80x9cDxe2x80x9d pillar of the vehicle. A linking arm is pivotally connected with the liftgate. A crank arm is pivotally mountable on the mounting bracket and pivotally connected with the linking arm. A gear train is pivotally mounted on said mounting bracket. A drive motor is mounted to the mounting bracket. The drive motor is operatively connected with the crank arm through the gear train. The gear train is movable between an engaged position and a disengaged position. The engaged position effects a driving engagement between the drive motor and the crank arm such that energizing the drive motor drivingly rotates the crank arm to responsively effect opening and closing of the liftgate. The disengaged position disengages the drive motor from the crank arm permitting movement of the crank arm without backdriving the drive motor. An actuator is operatively connected with the gear train and is operable to effect the movement of the gear train. A holding linkage is operatively connected between the gear train and the actuator to maintain the driving engagement once the actuator moves the gear train into the engaged position. A switch is mounted on the mounting bracket and is switchable in response to movement of the crank arm, indicating open and closed conditions of the liftgate. An electronic control unit electrically communicates with the body controller, the latch assembly, the drive motor, the switch and the actuator.